Processes and apparatus for recovering hydrocarbons from gas streams



W. M. PROCESSES AND APPARATUS'FOR RECOVERING May 2, 1961 DOW HYDROCARBONS FROM GAS STREAMS Filled Deo. 20, 1957 12 extending from the separator vessel 11 has connection with a three-way control valve 18 and said valve is, in turn, connected with the upper ends of the towers by lines 16a and 17a. Depending uponA the position of the three-way valve, gas flow is to either one or the other of the towers 16 and 17.

Assuming that the gas ow is through tower 16, said gas contacts the adsorption material therein and such material has an adsorbing efficiency for the lighter hydrocarbons such as propane, butane and gasoline fractions. The gas is conducted from tower 16 .through outlet line 16b, three-way valvelS! and outlet conductor 2t).V The` outlet conductor connects with a heat exchanger 21 and A*after passing through the heatexchanger, the gas is directed to sales or other disposition through the discharge line22. A Y

vWhile tower 16 ison an adsorbing cycle, a regenerating gas flows from a heater 23'through line 24, pastthree- .way valve 25.and into the tower 17. with this latter tower -being on a regenerating cycle. The regenerating gas is, .of course, heated and functions to regenerate or reactivate the bed within the .tower 17 by stripping or removing the hydrocarbons which were adsorbed by the bed during the preceding cycle. The heated regeneration gas. picks lup such hydrocarbons and carries them as vaporized liquids from .tower 17 through a line 26, past a three-way valve 27 andthrough conductor 28 to an atmospherictype heatexchanger 29. ,HeatY exchanger 29 functions 'to begin .cooling of the regenerating gas'fstreamand said stream is then conducted-through the Yline-30v to the lheat exchanger 21 where it is passed inv heat exchange relationship to the discharging main gas stream flowing through conductor 20v and discharge line 22. Further cooling of the regeneration gas is accomplished inthe heat exchanger 21 and said regeneration gas stream then passes .through conductor 31 to a liquid accumulator 32. The cooling of the gas by the heat rexchangers 29 and 21 results in `condensing the hydrocarbon fractions which .have been picked up by the gas and these condensed liquid fractions drop out of the regeneration gas stream as it ows through the liquid accumulator 32. The regeneration stream from which the liquids have been removed is then recirculated through line 33, pump 34 and line 35, back to the heater 23. The liquids are withdrawn from .the accumulator vessel 32 through a discharge line 36.

In the operation of the hydrocarbon recovery apparatus ,and process B, the towers 16 and 17 are alternately on an adsorbing and a regenerating cycle, this being accomplished by automatically actuating the various three-way valves 18, 19, 25 and 27 to switch the ows.- Thus, a substantially continuousprocess is obtained.

As has been noted, the liquids, which werefinitially separated from the main stream in the separator 11, are conducted from the lower portion of the separator through .discharge line 13 and into the upper portion of thesepa- 'rator-stabilizer vessel A. These liquids comprise the heavier hydrocarbons and are stable as liquids at the' particular operating pressures and temperatures.. It is desirable that the vessel A be operated at a lower pressure than the separator 11 whereby a ashing of the lighter constituents contained in theliquids conducted from the separator 11 will occur as said liquids are introduced into the upper portion of the vessel A. This ashing of the lighter constituents will further stabilize the liquids which, as will be explained, subsequently pass downwardly within the vessel A. It is pointed out that if necessary, Vde- .sred stabilization of the liquids separated in the separator 11 may be accomplished in any well known manner as,

.for example, by the application of heat which may be `carried out by mounting a heat exchanger in the discharge line 13. By heating, the liquid lighter constituents would be driven off vand would be separated from the liquid vwithin the upper portion of the vessel A.

n The separator-stabilizer vesselA is shown schematically and includes apseparating chamber 37 in its upper portion with a stabilizer section 38 therebelow. The lighter constituents contained in the liquid entering `the vessel through line 13 are separated in the separator section and escape from the upper end thereof through the conductor 37a, while the liquid ows downwardly through the stabilizer section 38. Said stabilizer section may be of any desired or conventional construction and, as illustrated, includes a plurality of inclined contact trays; said section may, if desired, employ the well known bubble tray arrangement or may be a packed section which functions to produce intimate liquid-gas contact.

The discharge line 36 extending from the liquid accumulator 32 of the adsorption apparatus B is connected into the lower portion of the separator-stabilizer A and a suitableoat-controlled valve 40 is disposed in this line, said valve bein-g actuated by a oat 41 located within the accumulator vessel 32 of the adsorption apparatus B. Thus, the hydrocarbons extracted vby the appafwill obviously'rise upwardly through the stabilizer'.section The heavier hydrocarbon liquids, which are substantially stable at the operating pressures and temperatures having been introduced into the upper end of the vessel A, flow downwardly through the stabilizer section 38 and "are thus directed in countercurrent ow to the vapors rising within said section. This results in the downwardly Nowing heavier hydrocarbon liquids intimately contacting. the upwardly owing Hash vapors and lighter fractions-as the same pass through the stabilizer section whereby the heavier, more stable liquids pick up the lighter vapors and fractions with the mixture passing downwardly to the bottom of the vessel A. Any of the Vextracted liquid, whichhas not vaporized upon entry rinto the vessel A will, of course, How downwardly to the bottom and the nal liquid product is discharged from vessel A through an outlet line 42. Any Hash vapors, which are not picked` up by thev countercurrent ow of V,the heavier. less volatile liquid, are discharged from the upper end of vessel A through the line 37a.

The liquid product escaping from the separatorstabilizer is a mixture of the initially separated heavier hydrocarbon liquids and the extracted lighter hydrocarbon liquids and provides a final product which is a stable liquid. This'stable liquid is conducted from-the vessel A through the discharge conductor 42 which has its opposite end connected to the usual stock tank 44. Flow through the discharge conductor 42 is controlled by a valve 43 which is actuated by a oat 45 mounted within the separator section of the separator-stabilizer vessel A. 4

From the foregoing it will be seen that the process Vcontemplates the treating of a two-phase stream, which `through a suitable hydrocarbon recovery apparatus and process, such as the adsorption apparatus and process B, lwherein the lighter, more volatile hydrocarbon constituents are recovered.. Thereafter, the initially separated liquid phase, which constitutes a liquid which vis heavier, rmore stable and less volatile, is directed in countercurrent ow to the vapors of the more volatile, lighter liquids, which have been extracted by the adsorption process B. The separator-stabilizer vessel A is operated at a lower pressure than is the adsorption unit A so that a ashing of the extracted, more volatile liquids will occur and the flashed vapors, moving in countercurrent How to the heavier liquids, are picked up .by said liquids and become a party thereof.- The liquid removed from the Y Y :lower -end of the stabilizer A fis 1in Aa `stabilized' Ycondition and may 'be conducted vtothe 'liquid stock tank l421 uinthe usual lmanner. Having been stabilized, the. loss Afrom Vaporization in the stock tank is minimized and the nal result is anI increased recoveryfof the desirable hydrocarbon constituents.

Actual practice has sh'own that vrecoveries havebeen substantially doubled by the use of the process `,herein disclosed. A`s` an example, where the accumulated 'liquids are, .conducted "from the Vvaccunlulator vvessel '32 of :the adsorption apparatus B "directly 'to "the stock tanks,a given gas 'streamprovided afhydrocarbon liquidrecovery of -13.2 barrels per "day, Where this same vgasfstrearn 1wlas'treate'd Aand its'hydrocarbon liquid `recovery was conductedtofthe separator-stabilizer vessel "A andcontacted with 100 barrels per day of the heavier liquids owing from separator 1l, the recovery of the hydrocarbon liquids from the gas stream was increased to 27.8 barrels per day. The difference in this recovery is accomplished by contacting the lighter, more volatile hydrocarbons, which are extracted from the gas in the adsorption appav ratus B, with the heavier previously separated, less volatile liquids in the separator-stabilizer vessel. The heavier liquids contacting the lighter liquids in countercurrent ow pick up the more volatile fractions which would otherwise escape to atmosphere and the liquid llowing from theA stabilizer vessel A is in a stabilized condition providing a stable liquid product which will remain in the stock tank.

As has been noted, any suitable adsorption process or apparatus may be employed in place of the particular apparatus and process B which is schematically illustrated in the drawing. So long as the two phase stream is first separated, after which the gas is treated tot exv but also the separator l1 and the separator-stabilizer A,

are subject to variation in details of construction.

The foregoing disclosure and description of the invention is illustrative and explanatory thereof and various changes in the size, shape and materials, as well as in the details of the illustrated construction, may be made within the scope of the appended claims without depart-V ing from the spirit ofthe invention.

What I claim is:

1. The process of recovering hydrocarbon liquid fractions from a ma'n hydrocarbon stream which has a portion of its constituents in the gas phase and the remainder thereof in the liquid phase, said process including, separating the gas from the hydrocarbon liquids in said main stream, thereafter subjecting the separated gas to an adsorption process wherein said gas is directed through an adsorbent bed to extract hydrocarbon liquid fractions which are more volatile than the hydrocarbon liquids which were separated from the main stream, recovering the extracted liquid fractions as a liquid product, ashing vapors from said liquid product and thereafter intimately contacting the ash vapors from the liquid product with said liquids which were initially separated from the man stream by directing said flashed vapors in countercurrent flow to the initially separated liquids whereby the initially separated liquids absorb a portion of said ash vapors to produce a stable liquid product.

2. The process of recovering hydrocarbon liquid fractions from a main hydrocarbon stream which has a portion of its constituents in the gas phase and the remainder thereof in the liquid phase, said process including, separatfng the gas from the hydrocarbon liquids in said main stream, thereafter subjecting the separated gas to an adsorption process wherein said gas is directed through an adsorbent bed to extract hydrocarbon liquid fractions which are more volatile than the hydrocarbon t 6 t Y ,t liquids'whi'chwerc separated from the main stream, recovering t'he'extracte'd-liquid fractions vfrom vthe bed as a liquid product, Iconducting the liquids which -were ini-l tially separated -from, the ymain stream into a closed zone and-directing the same ldownwardly within said zone, and conducting the liquid 4product 'which was recovered by the adsorption pro-cessv into the lower portion of said zo'neto causetheiflashed vapors vfrom theliquid product toow upwardly iii-countercurrent ow to the separated liquids, whereby the 1initimate contact' therebetween l produces a lstable 'liquid product.

"3. The process as s et forth in claim 2, together with theadditio'nal steps `tof-conducting the stable liquldproductfromthedower end of the closed zone tostorage, and discharging vapors ffromf-the upper end of said zone.

4. The process of recovering hydrocarbon liquid fractions from a mainhydrocarbon stream having a portion thereof in the gas phase and the remainder thereof in a liquid phase, said process including, conducting the main stream to a separating zone to separate the gas from the liquid in said main stream, directing the separated gas through an adsorption zone, extracting within said zone hydrocarbon liquid fractions which are more volatile than the l.quids initially separated from the main stream, recovering from the bed the extracted liquid fractions as a liquid product, conducting the initially separated liquids linto a stabilizing zone to stabJiZe the same, owing the stabilized liquid in a downward direction within a contacting zone, conducting the recovered liquid product to a ashing and separating zone to separate flash vapors from the liquid product, directing the ashed vapors upwardly within the contacting zonein countercurrent ow to the downwardly owing stabilized liquids, whereby said liquids intimately contact said vapors to pick up the same, and discharging said liquids having flashed vapors absorbed theren from the contacting zone.

5. The process as set forth in claim 4, together with the additional steps of withdrawing the liquid product from the ashing and separating zone, and mixing said liquid product w.th the liquids discharged from the contacting zone to produce a stable liquid product.

6. An apparatus for recovering hydrocarbon liquid fractions from a main two phase stream which includes,

a separator for separating the gas from the liquids in sajd main stream, a hydrocarbon recovery adsorption apparatus having means for extracting and recovering hydrocarbon liquid fractions from the gas as a liquid product, means for directing said separated gas through said apparatus to produce a liquid product which is more volat le than the liquids separated in the separator, means for stabilizing the liquids owing from the separator, means for separating the vapors which are capable of flashing from the liquids of the liquid product produced in the adsorption apparatus, a vessel having a contacting zone, means conducting the stabilized liquids which were separated in the separator and stabilized into the upper portion of the contacting zone of said vessel, whereby sa.d liquids ow downwardly therein, means conducting the flash vapors which were separated from the liquid product into the lower portion of the contacting zone of the vessel whereby said flash vapors flow upwardly and are intimately contacted by the downwardly flowing liquids to produce a stable liquid product, and means for conducting said stable liquid product from said vessel.

7. An apparatus as set forth in claim 6, with means for mixing the separated liquid ofthe liquid product with the stable liquid discharged from said vessel.

8. An apparatus for recovering hydrocarbon liquid fractions from a main two phase stream which includes, a separator for separating the gas from the liquids in said main stream, a hydrocarbon recovery adsorption apparatus having means for extracting and recovering hydrocarbon liqu'd fractions from the gas as a liquid product, means for directing said separated gas through said apparatus to produce a liquid product which is more volatile than'the liquids separated in the separator, a vessel having an upper stabilzing and separating'zone,

acontacting/zone andv alowerashing and separating zone, means conducting the liquidswhich were separated lin the separator into the upper stabilizing and separating zone to ash vapors and thereby stab.lize the liquids, said stabilized liquids flowing downwardly through the contacting zone of the vessel, means conducting the liquid product which was produced by the adsorption apparatus into the lower ashing and separating z one to` ash vapors from the liquid product, said flashvapors owing upwardly Within the contact zone of the vessel in countercurrent flow to the downwardly owing liquidsto intimately contact said vapors with said liquids to recover a portion of the ash vapors by means of the liquids, 15 2,886,123

y8 said liquids passingdownwardly into the lower flashing and separating zone within the vessel to adminw'thfthe liqu.ds of said liquidv product, and mixed liquids fromthe vessel.

References Ctedin the fileof this patent Y UNITEDA sTATEsPA-IENTS Weir .L. Aug. 3, 1926 2,719,816 Rich Oct. 4, 1955 2,760,905 MacLars'en Aug. 28, 1956 2,769,754' Sweetser. et al. Nov.v '6, 1956 2,318,133 Rosenthal Dec.- 31,1957 2,859,173 Hess'etl al. Nov. 4, 1958 Miller etal.l May 12,1959 

1. THE PROCESS OF RECOVERING HYDROCARBON LIQUID FRACTIONS FROM A MAIN HYDROCARBON STREAM WHICH HAS A PORTION OF ITS CONSTITUENTS IN THE GAS PHASE AND THE REMAINDER THEREOF IN THE LIQUID PHASE, SAID PROCESS INCLUDING, SEPARATING THE GAS FROM THE HYDROCARBON LIQUIDS IN SAID MAIN STREAM, HEREAFTER SUBJECTING THE SEPARATED GAS TO AN ADSORPTION PROCESS WHEREIN SAID GAS IS DIRECTED THROUGH AN ABSORBENT BED TO EXTRACT HYDROCARBON LIQUID FRACTIONS WHICH ARE MORE VOLATILE THAN THE HYDROCARBON LIQUIDS WHICH WERE SEPARATED FROM THE MAIN STREAM, RECOVERING THE EXTRACTED LIQUID FRACTIONS AS A LIQUID PRODUCT, FLASHING VAPORS FROM SAID LIQUID PRODUCT AND THEREAFTER INTIMATELY CONTACTING THE FLASH VAPORS FROM THE LIQUID PRODUCT WITH SAID LIQUIDS WHICH WERE INITIALLY SEPARATED FROM THE MAIN STREAM BY DIRECTING SAID FLASHED VAPORS IN COUNTERCURRENT FLOW TO THE INITIALLY SEPARATED LIQUIDS WHEREBY THE INITIALLY SEPARATED LIQUID ABSORB A PORTION OF SAID FLASH VAPORS TO PRODUCE A STABLE LIQUID PRODUCT. 